In this paper, F. Wible and H.-G. Lehner provide the conclusions of a report on the excavation conducted in the parish church of Martigny, the capital of Valais in Roman times and bishopric from the fourth to sixth century. The parish church lies outside the Roman town o/Forum Claudii Vallensianum. The first likely Christian building included two rooms, each with an eastward-facing exedra, belonging to an unidentified Roman building. In one of them, there was a pool which the authors think was a baptistery, whereas the condition of the other does not allow us to interpret its function. The first clearly double church, in the end of the fourth century, consisted of two rectangular rooms (15,40 x 7,70 north and 15,40 x 6 south) further extended by rectangular apses. The excavation revealed the complex development of the church: the baptistery, first included in the south church, was removed when the apse, which had a passage outside, was built; traces of later installations were also noted: a chancel screen in the north church, a semi-circular wall inside the two apses, a portico or gallery in front of the west side, additional constructions (parekklesion ?); one of which is a long narrow building with an absidal chapel, full of graves. In Carolingian times, the north church was rebuilt but the south church was deserted; later, the plan of the Romanesque church was still a double church with a large nave and only one aisle with an apse. In the seventeenth century, this arrangement completely vanished in a now westwardfacing church.